90 



THE AGRICULTURAL NEWS. 



March 24, 1917. 



INSECT NOTES. 



THE SUGAR-CANE FROGHOPPER IN 



GRENADA. 



Froghoppers were first recorded from Grenada in 1895 

 by Uhler, under the name of Tomaspis pictipennis, but at 

 that time they were apparently of no economic importance. 

 In 1912 they were found on Para grass, and specimens were 

 «ent through the Imperial Department to the Board of 

 Agriculture in Trinidad. Mr. I'rich. the Entomologist, 

 considered them to be different from the Trinidad, species, then 

 known as Tomaspis tiaria, and was of opinion that this insect 

 might be capable of attacking sugar-cane. Towards the end 

 of 1916, froghoppers were reported as doing considerable 

 damage to sugar-cane on one estate. 



Mr. C. B. Williams the Entomologist in charge of the 

 frogbopper investigations in Trinidad paid a visit to Grenada 

 in December 191G, and the results of his investigations were 

 subsequently publishi d in a 1 rief report. Mr. Williams, 

 after comparing a number of the froghoppers from Grenada 

 with the Trinidad species attacking sugarcane, states that 

 he can find no constant difference Ijetween them, and there- 

 fore the Grenada species must bear the same name as the 

 Trinidad species, Tomaspis sacharina, Distant. 



He found froghoppers either on sugar-cane or on grass 

 in several different localities throughout the island, showing 

 without a doubt that they had been established there for 

 many years. Actual damage to the canes was reported 

 from two e.states, and on one of these the injury was fairly 

 severe. In this instance three fields were attacked, two of 

 these being badly affected, the third only suffering .slight 

 damage. Mr. Williams further points out that 'all the fields 

 attacked were at a comparatively high altitude, 4()O-.50Ofeet, 

 on steep slopes and exposed to the East trade wind. They 

 were strikingly different from the type of field most liable 

 to frogbopper attack in Trinidad.' Another point of interest 

 in connexion with this outbreak is that the worst attacked 

 field on this same estate had been alternately put under cane 

 and pasture during the last ten years, and the two other fields 

 had been under pasture for the same period and had only 

 this year been put under cane. 



Mr. Williams also found slight attacks of frogbopper in 

 low-lying fields in other parts of Grenada, but there was no 

 injury to the cane. 



From observations made by Mr. Uriah in Trinidad, it has 

 been noticed that the conditions most favourable to the devel- 

 opment of the froghoppers are found in cane- fields where there 

 16 sufficient grass without an excessive amount of moisture 

 If, however, the surroundings are exceedingly dry, and exposed 

 to wind and sun, the nymphs cannot surround themselvee 

 with a protection of spittle, and soon die; and on the other 

 hand, if there is too much moisture, the froth becomes too 



watery to suit the immature frogbopper. It is also known 

 that frogbopper nymphs breed freely in lands which have 

 been allowed to run to grass, and in this instance it would 

 seem probable that the alternation of grass and cane, and the 

 consequent difficulty of keeping the cane-fields clear of weeds 

 and gra.ss tend to produce conditions favourable to the 

 development of the frogbopper nymphs. 



In Trinidad it has been recommended that cover crops 

 be planted on ploughed land to keep down grass. It is not 

 however, always practicable to plant a large area with cover 

 crops, in which case a border of about 100 feet can be 

 planted on abandoned fields adjacent to canes. In any case 

 the practice of clean cultivation in and around the cane-fields 

 will always help to keep down the numbers of froghoppers. 

 The practice of heaping up the soil around the cane stools 

 seems to be of doubtful value as a preventive measure against 

 the froghoppers, since the soil while it remains encourages 

 a growth of cane roots. When the soil is washed away by 

 rains the exposed roots form an attraction for these pests. 

 The mixing of lime with the soil heaped up around the stools 

 seems to be of some value in warding off an attack, but can 

 only be a temporary measure. 



In the course of his investigations in Grenada, Mr. Wil- 

 liams made a careful search in order to ascertain whether 

 any of the natural enemies which are proving so useful 

 against the frogbopper in Trinidad were also present in 

 Grenada to the extent of serving as a means of control. He 

 examined several hundred spittle masses without finding 

 a single syrphid Hy larva, so that they cannot be 'present in 

 numbers sufficient to be of any value as a control.' The 

 larvae of the syrphid tty [Salpingogaster nigra, Schiner) have 

 come to exercise a considerable check on frogbopper nymphs 

 in Trinidad, owing to successful artificial breeding and 

 distribution throughout the frogbopper territory. 



Another natural enemy of the frogbopper in Trinidad, 

 the green muscardine fungus (Metarrhidum anisopliae) has 

 apparently not become sufficiently well established in 

 Grenada to be of any value against the frogbopper. One 

 adult frogbopper was found infected with the early stage of 

 this fungus. Mr. Williams, however, took with him to 

 Grenada some of the spore mixture of this frogbopper fungus 

 and distributed this over a part of the badly infested fields 

 with the idea of starting a colony in ( Grenada. The results 

 of this experiment will be awaited with interest. 



As regards some of the other natural enemies of the frog- 

 hoppers, it may be mentioned that spiders belonging to the 

 family Attidae were scarce, and that only a few specimens 

 of the predaceous grasshopper, Xiphidium sp., were found 

 in the grass near the cane-fields. These grasshoppers appar- 

 ently do not actually enter the cane plots. 



The frogbopper situation in (Jrenada need cause no 

 alarm at present, but these insects will require careful 

 watching. Such measures as weeding, the subsequent removal 

 of the heaps of weeds from the cane-fields whenever possible, 

 the burning or removal of trash, and the covering of resting 

 fields with some kind of cover crop all contribute towards 

 preventing the spread of froghoppers. As can be seen from 

 the observations ma'le by Mr. Williams, the natural enemies 

 of the frogbopper <\c not play a very important part in the 

 control of this pest, and the time may come when the artificial 

 introduction of soiiio of these enemies from other countries will 

 have to be undertaken. Meanwhile tho.se that are already 

 present should ht'. encouraged in every way possible. 



J.C.H. 



